Reader question: Which costs are shared after a newly installed gas heating system that falls under the rules from 2028 or 2029 respectively?
In the German rental building a new gas heating system is to be installed in 2026. For your household planning it is asserted that the landlord will in future “cover half of the heating costs”. That is too imprecise for a reliable calculation. The current §5a CO₂KostAufG concerns certain costs after a covered installation and specifies different start dates. [CO2KostAufG5a]
The text is a preparation for future statements of account according to the legal status of 17 October 2026. Before the respective later year it must be checked whether the regulation still applies unchanged. No energy prices or savings are being forecast.
Assign the actual installation to the plant
§5a links to systems pursuant to §43 paragraph 1 GModG in existing buildings. This connection to a system includes certain gas, heating oil or liquefied gas heating systems newly installed after 29 July 2026. [CO2KostAufG5a][GMODG43] The article considers a gas case, not a technical recommendation for a new heat generator.
Please provide the plant designation, the actual installation date and the building allocation. A repair invoice or a general replacement plan does not yet confirm all prerequisites. For new builds §5b provides its own limited scope of application; the existing-building constellation is not automatically transferred to every newly constructed house. [CO2KostAufG5b]
Separate three cost positions with two start years
For the covered case §5a specifies the halving of gas network charges and carbon dioxide costs from 1 January 2028. For certain fuels that are mandatorily used in part the sharing begins on 1 January 2029 and concerns a fuel share of up to 30 percent of the total fuel consumed. [CO2KostAufG5a]
These groups belong in separate lines of your planning. “Halving” does not result in half of the complete gas bill including all other components. A rent increase because of the investment is a different claim and is not entered in the same line.
Fictitious enquiry before a budget commitment
A tenant party receives a non-binding cost preview for a planned installation in autumn 2026. In it the total expected gas bill for 2027 is halved. Neither network charges nor carbon dioxide costs are listed separately. All occurrences are invented.
They do not accept the halving as a secured relief. Instead they ask about the plant reference, the cost components taken into account and the assumed first billing year. The answer should make clear which amounts are factual information and which are mere price assumptions. The case deliberately does not calculate an allegedly final monthly payment amount.
Disclose failure and transition period
§5a paragraph 4 contains exceptions with twelve-month periods for certain installations following irreparable failure and additionally refers to §43 paragraph 7 GModG. [CO2KostAufG5a][GMODG43] Therefore present such a replacement with the failure date, installation time and previous duty status for individual review. The term “emergency replacement” alone does not confirm every statutory exception.
Distinguish billing and self-supply
Where supply is via the landlord the later annual heating cost statement is central. For legally covered self-supply §5a contains its own calculation rule for the tenant side. [CO2KostAufG5a] Therefore collect the invoice of the contract partner who actually bills and record the supply route.
The result is a comprehensible enquiry on the plant, cost type and timing. A future relief remains marked as an assumption until the calculation is clarified. Ongoing payments are not unilaterally halved solely because of a shortened advertising statement.